The present disclosure relates to an image forming apparatus including a mechanism that uses a cleaning member to remove residual toner remaining on a surface of an intermediate transfer belt, and in particular, relates to a method for preventing removed toner from adhering to the intermediate transfer belt again.
Conventionally known image forming apparatuses adopting an intermediate transfer method include an endless intermediate transfer belt which is caused to rotate in a predetermined direction and a plurality of image forming portions arranged along the intermediate transfer belt; the image forming portions form toner images of respective colors, which are primarily transferred sequentially onto the intermediate transfer belt to be superimposed one on another, and then secondarily transferred onto a recording medium.
In such image forming apparatuses adopting the intermediate transfer method, there is arranged a belt cleaning device to remove residual toner from the intermediate transfer belt after the secondary transfer is completed. In a case where the intermediate transfer belt does not include an elastic layer, a blade method is adopted in which toner is scraped off the intermediate transfer belt by pressing a cleaning blade against a surface of the intermediate transfer belt.
On the other hand, in a case where the intermediate transfer belt includes an elastic layer, a cleaning device is often adopted which includes a cleaning brush which mechanically and electrically collects toner remaining on the surface of the intermediate transfer belt, a collection roller which collects toner from the cleaning brush, a blade which scrapes toner off a surface of the collection roller, and a spiral conveyor which conveys toner scraped off the surface of the collection roller into a waste toner collection container.
There have also been proposed various techniques to adjust conditions for cleaning of intermediate transfer belt; for example, a technique is known in which an adjustment mechanism is used which adjusts contact conditions in which a cleaning member and an intermediate transfer belt contact each other, in order to adjust the contact conditions to be suitable in each of a monochrome mode and a color mode.
There is also known a technique for preventing soiling of the back of a recording medium, in which, in switching from color mode to monochrome mode, primary transfer means of each image forming portion is once released from a state in which it is pressed in contact with an intermediate transfer belt and then the primary transfer means of such one of the image forming portions in which image forming is performed in the monochrome mode is pressed into contact with the intermediate transfer belt.